Recently, a storage device including a nonvolatile memory has become widespread. A solid state drive (SSD) based on NAND flash technology is known as a storage device of one such type. Such an SSD is used as main storage of various computers because of its low power consumption and high performance. For example, a server computer having some tens or some hundreds of the SSDs (enterprise SSDs) is operated at a data center.
For a storage device including the SSDs, lower total cost of ownership (TCO) and higher quality-of-service (QoS) are demanded. To meet these demands, a host of the storage device may need to more actively manage and control operations of the storage device.